Parts feeders used in the manufacturing industry are well known. Typically, such parts feeders comprise bowls or hoppers containing a bulk source of parts. The parts are delivered to a conveying apparatus which is intended to aid in separating the parts. The use of vision-based flexible parts feeders is a relatively new phenomenon in the manufacturing industry which is gaining credibility. With the use of such vision-based parts feeders, companies are able to make their manufacturing systems more flexible in order to cost effectively automate the production of smaller volume products. Typically, in operation, such parts feeders deliver bulk parts from a source to a transport surface for inspection and subsequent picking therefrom by a robot. Preferably, a single camera is used to inspect the separated parts on the transport surface. The inspection is primarily used to identify which parts may be successfully grasped by the robot as well as the location of each identified "pickable" part.
In general, the "flexibility" of a vision-based flexible parts feeder is closely related to the ability of the lighting system to illuminate the widest range of part types in a way that permits successful object recognition by the camera understanding that the different part types are randomly oriented. One flexible parts feeder known in the prior art is the Flexfeeder 250 manufactured by Adept Technologies of San Jose, Calif. This particular feeder comprises a translucent belt on which parts are placed for inspection by a downward-looking camera. Light is projected from the underside of the translucent belt which is more commonly known as back-lighting. This lighting method is relatively common and is a very robust means to illuminate a wide variety of parts including parts which have very little color contrast with the belt. However, in many cases where parts possess a profile symmetry, no distinction can be made by the camera as to whether or not the part is right side up or upside down since the image seen by the camera is only its silhouette or perimetric shape. One example of a such a part with perimetric symmetry is a small gear with an axially extending hub on one side. Due to lighting conditions, the back-lighting of the Flexfeeder 250 does not permit a distinction to be made between such a gear with the axially extending hub facing upward and such a gear with the axially extending hub facing downward.
Another flexible parts feeder known in the art is the programmable reconfigurable parts feeder manufactured by Intelligent Automation Systems, Inc., of Cambridge, Mass. This particular parts feeder also utilizes a translucent belt on which parts are placed in single file for inspection by a downward-looking camera. In addition, a mirror is located next to the part inspection location and tilted at 45 degrees. This allows a "second view" without the need for adding another camera. Depending on the specific part geometry, this may or may not provide the information needed to determine actual part orientation because the shape of the "second view" of the part may vary with orientation of the part about its vertical axis.
U.S. Pat. No. 5,280,170 to Baldwin teaches an inspection machine wherein a vertically standing container is transported to an inspection location on a transparent conveyor. There is a diffuser plate located beneath the transparent container. A beam of collimated light is directed vertically downward toward the diffuser plate and a two-dimensional camera actually views the shadow of the container cast onto the diffuser plate and the image is processed to evaluate circumference of the container. Thus, Baldwin's machine has the capability of only viewing the silhouette. Orientation of the vertically standing container is known prior to inspection.
The prior art fails to teach a method or apparatus wherein parts can be visually inspected by a single camera such that randomly oriented parts (there may be several different types of parts present) can be identified and further, the side-up orientation of such parts can be determined.